1. Field of the Invention
This invention relates to driving a gas discharge panel with a shift or scan function for the discharge spots, and in particular, to new driving circuits and improved shifting methods for the self-shift type plasma display panel having a regularly arranged multi-phase discharge cell array.
2. Description of the Prior Art
AC driven gas discharge panels with a shift or scan function for the discharge spot are well known as "self-shift plasma display" panels. One such self-shift plasma display panel is described in detail in U.S. Pat. No. 3,944,875 to Owaki et al., entitled "Gas Discharge Device Having a Function of Shifting Discharge Spots", and an improved panel, in which the insulated crossover configuration for connecting the shift electrodes to the buses is eliminated, is described in co-pending U.S. Patent Applications Ser. Nos. 810,747 and 813,627 to Yoshikawa et al. The basic configuration of such prior art self-shift plasma display panels includes a plurality of shift electrodes arranged with regularity on the substrates adjacent to the gas discharge space with discharge cell groups corresponding to at least three phases defined between opposing portions of electrodes, and the shift electrodes are led out to terminals via buses corresponding to the phase grouping of said discharge cells. Thus, by applying voltage pulses to these buses in a specified sequence, discharge spots generated in accordance with input data can be shifted sequentially between adjacent dischage cells.
However, in order to implement such a drive function, at least two kinds of voltage pulses are necessary, one a comparatively wide voltage pulse for shifting the discharge spot and the other a comparatively narrow voltage pulse for erasing the wall charge remaining at the discharge cell from which a discharge spot was transferred, and it is necessary to appropriately combine these voltage pulses into pulse trains and to sequentially supply them to each bus.
The method generally used to distribute these voltage pulses involves preparation of gate signals corresponding to the at least two kinds of pulses to be combined. These gate signals are prepared for each bus with individual phase, and multi-phase driving pulse trains are obtained by this gating. However, in such gate-control systems, when the number of phases or of buses to be driven increases, or if the number of pulses to be applied to each bus in every unit period increases, with prior art methods nonuniformities develop between each phase, and also the pulse train to be supplied sequentially to each phase becomes asymmetric; therefore circuit design for driving and timing control becomes very difficult. This difficulty in control arises particularly with the self-shift type gas discharge panel having the meander electrode configuration which is proposed in the above cited co-pending U.S. Patent Application Ser. No. 813,627 and which is discussed below.